I built a Senorita several years ago (still have it) using 1/4" hard balsa push rods. I don't know how many times its been flown with absolutely no problems.
Goboto- Surely your push rod is binding somewhere. The elevator rod exits right out the rear of the fuse, supported only by the servo arm and the elevator control horn. Have you tried moving the clevis out to the last hole in the horn? I can't remember what the elevator travel is, but it isn't much. When you get it ironed out, you'll have one great flying airplane- Jim